ETC AB-055

APPLICATION BULLETIN
®
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IMPROVE OPA541 CURRENT-LIMIT STABILITY
By Hubert Biagi (602) 746-7422 and R. Mark Stitt
OPA541 is the industry’s highest performance monolithic
power amplifier. It can operate on ±40V power supplies and
put out 5A continuously (10A peak). Internal current-limit
circuitry can be user-programmed with a single external
resistor to protect the amplifier and load from fault conditions.
CALCULATING CURRENT LIMIT RESISTOR VALUE
OPA541M
R
0.08 to 0.16
0.17 to 0.77
0.78 to 10.0
R1
(Ω)
C1
(µF)
10 to 5
5 to 1
1 to 0
0.68(1)
1.3(1)
2.7
0.68
0.33
0.068
0. 809
− 0. 057
I
CL
R
CL
=
0. 813
− 0. 020
I
CL
Where:
RCL = Current limit resistor (Ω)
ICL = Current limit (|A|)
The compensation circuit consists of an R, C network
connected to the amplifier drive output as shown. Component values for the network depend on the output current
limit desired. Table I below shows recommended values.
RCL
(Ω)
=
OPA541P
Under some conditions, the OPA541 may oscillate during
current limit. In some applications, this is acceptable. However, you can improve stability during current limit by
adding external compensation as shown in Figure 1.
CURRENT LIMIT
(A)
CL
NOTE: (1) You can use two or four parallel connected 2.7Ω resistors to
make 1.3Ω or 0.68Ω.
TABLE I. R 1, C 1 Network Values for OPA541—
see Figure 1.
V+
+In
–In
Current
Sense
R CL
Output
Drive
VO
R1
C1
OPA541 Power Amp
V–
FIGURE 1. An R1, C1 network can be added to the OPA541 output to improve stability during current limit.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.

1993 Burr-Brown Corporation
AB-055
Printed in U.S.A. May, 1993